23 here.
Platinum on AA since 97
Premier Exec on United since 99
Platinum on Starwood since the program started
Diamond on Hyatt JUST THIS YEAR!! YEAH!
Gold on Hilton just this year as well.
I usually am dressed down (jeans, tennis shoes, untucked shirt, hat, etc.) when traveling to my jobs on Sundays and have found that the service does not differ if your attitude is that of an experienced traveler.
I found my age to be an advantage when dealing with younger staff members of the hotel and airlines I frequent. I still keep in touch with a few of them.